1. Field of the Invention
This invention relates to photoelectric type solar tracking systems, and particularly to a system for maintaining a solar collector with its responsive surface normal to the sun as the sun traverses the sky from sunrise to sunset.
2. General Description of the Prior Art
Solar collectors, typically panels 18 to 24 inches in width and six to ten feet in length wherein either air or liquid is heated by the sun, are generally tilted along their length to the latitude of use. For improved efficiency, they should also have their responsive surface maintained normal to the sun's rays as the sun traverses the sky from east to west. This is particularly so, if not a must, with concentrating type collectors. Thus, it is well known to rotably mount a solar collector about a north-south axis and to by some means rotate it from east to west to follow the sun. Typically, such a means includes a pair of photocells mounted on the solar collector, one of which views the eastern quadrant (90.degree.) of the horizon (when the collector and cells are positioned with their responsive area in a horizontal plane), and one of which views the western quadrant of the horizon. A difference in outputs between the cells indicates an error point at the sun, and thus the outputs of the cells may and are used to correctly position a collector. The applicants have found, however, that this capability alone is insufficient. Particularly they have observed that clouds, particularly a single bright cloud, can draw a photocell pointing away from pointing at the sun and causes a drive system to erronously point a collector.